Method and apparatus for downhole fluid analysis for reservoir fluid characterization

Abstract

A formation fluid sample is exposed to a rigidly-supported semi-permeable membrane such as silicone rubber to permit diffusion of gases and vapors from the formation fluid into a vacuum chamber, while at the same time, blocking the passage of any liquids. The membrane-transmitted gas is analyzed in the vacuum chamber by a residual gas analyzer. An ion pump or sorbent is associated with the evacuated chamber to maintain the vacuum. The ion pump or sorbent removes gases and vapors from the chamber that diffuse into the chamber from the reservoir sample that is on the opposite side of the semi-permeable membrane.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This patent application claims priority from U.S. provisional patent application No. 60 / 553,921 entitled A Method and Apparatus for Downhole Fluid Analysis for Reservoir Fluid Characterization by Rocco DiFoggio, filed on Mar. 17, 2004 which is incorporated herein by reference in its entirety.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates generally to downhole reservoir characterization and in particular to a method and apparatus for real time identification of gases diffused out of a formation fluid sample. Formation fluid samples are obtained and gases are allowed to diffuse from these fluid samples through a semi-permeable membrane into an evacuated chamber. The gases are analyzed in the evacuated chamber by a mass spectrometer or residual gas analyzer (RGA) and a processor which identifies and distinguishes between gases such as C1–C5, H2S, C02, N2 and other gases or vapors present in a do...

AI Technical Summary

Benefits of technology

The present invention provides a method and apparatus for real-time detection, distinction, and quantification of gases and vapors in downhole formation fluids. This is achieved by using a semi-permeable membrane to block liquids but allow passage of certain gases and vapors, which are then analyzed by a residual gas analyzer (RGA) in a vacuum chamber. The invention can detect and analyze vapors associated with oil-based drilling fluid, providing a real-time estimate of the percent contamination of the sample by drilling fluid filtrate. The invention can also separate the gas from the fluid using a membrane and select from among multiple membranes with different thicknesses or compositions for gas diffusion. The gas can include vapors.

Problems solved by technology

Commercial development of hydrocarbon fields requires significant amounts of capital.

It is time consuming to retrieve fluid samples downhole and send them to a surface lab for analysis of gas content Moreover, surface analysis requires removal of the fluid sample and the tool from the borehole for testing the sample before additional exploration and / or production activities occur.

Images